The present invention relates to a new and improved construction of protective grating or screen, especially a protective screen for drift sand or the like, for an electrical air-cooled machine, comprising essentially vertically arranged profile ledge members or profile members disposed at least in two rows.
In the case of rotating electrical machines, which suck-up cooling air from the ambient surroundings, the air inlet- and outlet openings are arranged either directly at the machine housing or at a weather protective cabinet which is mounted upon the machine. The weather protective cabinets serve for mounting air filters and sound dampening devices. In those instances where the rotating electrical machinery is inherently aerated, only limited pressure differences are available for transporting the cooling air. It is therefore necessary that all elements of the cooling air-guide arrangement, part of which also is constituted by the protective devices at the inlet- and outlet openings, exhibit extremely small pressure losses. If there is required protection against so-called drift or blown sand, then there is employed a sand separator grating or screen which consists of mutually offset V-profile members. Such drift sand-protective screen or grating has been disclosed, for instance, in the brochure "L+M Ansaug-Luftungs-Jalousie" appearing in Lufttechnik + Metallbau AG, Wettingen, Switzerland. Such screen or grating should produce extremely small pressure losses, so that when generating the same pressure the machine ventilators or fans can convey larger cooling air currents through the machine. If this is not necessary then the weather protection cabins can be constructed smaller.